Dissolution of Cellulose in Mixed Solvent Systems

ABSTRACT

A method for dissolving cellulose in which the cellulose based raw material is admixed with a mixture of a protic intercrystalline swelling agent and an ionic liquid at a temperature of 25° C. to 180° C. for a time sufficient to dissolve the cellulose based raw material. The molar ratio of protic intercyrstalline swelling agent to ionic liquid may be 0.05 to 1.5 moles of protic intercrystalline swelling agent to 1 mole of ionic liquid.

This application claims priority from Provisional Application 60/976,221filed Sep. 28, 2007.

FIELD

This application relates to the dissolution of cellulose in a mixture ofdipolar aprotic intercrystalline swelling agents and ionic liquids.Further, it relates to the dissolution of cellulose in a mixture ofprotic intercrystalline swelling agents and ionic liquids.

DESCRIPTION

As the current world demand for cellulose increases, there is anincreasing demand for low cost raw materials which can be used incommercial processes that use these raw materials. Additionally, thereis a need to develop new processes which use these raw materials andwhich are simpler, have less of an environmental impact and do not havesome of the shortcomings of the current processes.

Solvents for the dissolution of cellulose and other constituents intrees and other woody and non-woody plants are increasingly important inorder to maximize the utilization of the components in their entirety.Increased use of textiles, fibers, films, membranes and other productsdictate the need for new solvent systems which can help meet demands inthese areas. Manufacturing facilities with these solvent systems must behave low capital costs and must meet environmental and regulatory laws.

Currently rayon and lyocell are commercially available cellulose fibers.Rayon is made in the viscose process. In the process, cellulose is firststeeped in a mercerizing strength caustic soda solution to form analkali cellulose. This is reacted with carbon disulfide to formcellulose xanthate which is then dissolved in dilute caustic sodasolution. After filtration and deaeration the xanthate solution isextruded from submerged spinnerets into a regenerating bath of sulfuricacid, sodium sulfate, zinc sulfate, and glucose to form continuousfilaments. The resulting viscose rayon is presently used in textiles andhas been used in such applications as tires and drive belts.

Cellulose is also soluble in a solution of ammonia copper oxide. Thisproperty forms the basis for production of cuprammonium rayon. Thecellulose solution is forced through submerged spinnerets into asolution of 5% caustic soda or dilute sulfuric acid to form the fibers,which are then decoppered and washed. Cuprammonium rayon can beavailable in fibers of very low deniers and is used almost exclusivelyin nonwoven wipe application.

The foregoing processes for preparing rayon both require that thecellulose be chemically derivatized or complexed in order to render itsoluble and therefore capable of being spun into fibers. In the viscoseprocess, the cellulose is derivatized, while in the cupramrnonium rayonprocess, the cellulose is complexed. In either process, the derivatizedor complexed cellulose must be regenerated and the reagents that wereused to solubilize it must be removed. The derivatization andregeneration steps in the production of rayon significantly add to thecost of this form of cellulose fiber and also possess environmentalissues in the use of zinc in coagulation baths and in the handling ofcarbon disulfide. Consequently, in recent years attempts have been madeto identify solvents that are capable of dissolving underivatizedcellulose to form a dope of underivatized cellulose from which fiberscan be spun.

One class of organic solvents useful for dissolving cellulose are theamine-N oxides, in particular the tertiary amine-N oxides. Lyocell ismade by dissolving cellulose in a mixture of N-methylmorpholine-N-oxide(NMMO) and water and extruding the solution into regenerating bath,usually water.

Lyocell is a generic term for a fiber composed of cellulose precipitatedfrom an organic solution in which no substitution of hydroxyl groupstakes place and no chemical intermediates are formed. Severalmanufacturers presently produce lyocell fibers, principally for use inthe textile industry. For example, Lenzing, Ltd. presently manufacturesand sells a lyocell fiber called Tencel® fiber.

Currently available lyocell fibers and high performance rayon fibers areproduced from high quality wood pulps that have been extensivelyprocessed to remove non-cellulose components, especially hemicellulose.These highly processed pulps are referred to as dissolving grade or highα (or high alpha) pulps, where the term α (or alpha) refers to thepercentage of cellulose remaining after extraction with 17.5% caustic.Alpha cellulose can be determined by TAPPI 203. Thus, a high alpha pulpcontains a high percentage of cellulose, and a correspondingly lowpercentage of other components, especially hemicellulose. The processingrequired to generate a high alpha pulp significantly adds to the cost ofrayon and lyocell fibers and products manufactured therefrom. Typically,the cellulose for these high alpha pulps comes from both hardwoods andsoftwoods; softwoods generally have longer fibers than hardwoods.

A wide variety of cellulose based raw materials can be used in thepresent application. Chemical pulp fibers used in the presentapplication are derived primarily from wood pulp. Other sources such asfrom kenaf and straw pulp may also be used. Suitable wood pulp fibersfor use with the application can be obtained from well-known chemicalprocesses such as the kraft and sulfite processes, with or withoutsubsequent bleaching. Softwoods and hardwoods can be used. Details ofthe selection of wood pulp fibers are well known to those skilled in theart. For example, suitable cellulosic fibers (chemical pulp fibers)produced from southern pine that are useable in the present applicationare available from a number of companies including Weyerhaeuser Companyunder the designations C-Pine, Chinook, CF416, FR416, and NB416. APrince Albert Softwood and Grande Prairie Softwood, manufactured byWeyerhaeuser are examples of northern softwoods that can be used.Mechanically and chemimechanically treated fibers such aschemithermomechanical pulp fibers (CTMP), bleached chemithermomechanicalpulp fibers (BCTMP), thermomechanical pulp fibers (TMP), refinergroundwood pulp fibers and groundwood pulp fibers can also be used.Examples of these pulps are TMP (thermomechanical pulp) made by Bowater,Greenville, S.C., a TMP (thermomechanical pulp) made by Weyerhaeuser,Federal Way, Wash., made by passing wood chips through three stages ofdual refiners, and a CTMP (chemi-thermomechanical pulp) obtained fromNORPAC, Longview, Wash., sold as a CTMP NORPAC Newsprint Grade with abrightness from 53 to 75.

Ionic liquids such as 1-ethyl-3-methylimidizolium acetate (EMIMAc) and1-butyl-3-methyl imidazoliumchloride (BMIMCl) are known to dissolvecellulose. It has now been found that the solubility of cellulose isincreased in mixtures of dipolar aprotic intercrystalline swellingagents and ionic liquids. Similar effects are noted when cellulose isdissolved in a mixture of a protic solvent and an ionic liquid.

Dipolar aprotic intercrystalline swelling agents include but are notlimited to dimethyl sulfoxide (DMSO), dimethyl acetamide (DMAc),N-methylmorpholine oxide, formamide, pyridine, acetone, dioxane,N-methyl pyrolidine (NMP), piperylene sulfone andhexamethylphosphoramide (HMPA). These dipolar aprotic intercrystallineswelling agents, by themselves, do not dissolve cellulose. In general,it is thought that liquids which produce a significant amount ofswelling are those that are capable of forming hydrogen bonded complexeswith the cellulose molecule. Dipolar aprotic intercrystalline swellingagents do not include imidazole based agents or amine based agents.

Protic solvents include but are not limited to water, low molecularalcohols such as methyl, ethyl, propyl, butyl and amyl alcohol, ethyleneglycol, acetic acid, methylamine, di- and triethylamine and butylamineand mixtures thereof.

As defined herein, ionic liquids are ionic compounds which are liquidbelow 100° C. A few ionic liquids for cellulose have melting pointsbelow room temperatures, some even below 0° C. The compounds are liquidover a wide temperature range from the melting point to thedecomposition temperature of the ionic liquid. Ionic liquids havecations or anions associated with the molecule. Examples of the cationmoiety of ionic liquids are cations from the group consisting of cyclicand acyclic cations. Cyclic cations include pyridinium, imidazolium, andimidazole and acyclic cations include alkyl quaternary ammomnium andalkyl quaternary phosphorous cations. Counter anions of the cationmoiety are selected from the group consisting of halogen, pseudohalogenand carboxylate. Carboxylates include acetate, citrate, malate, maleate,formate, and oxylate and halogens include chloride, bromide, zincchloride/choline chloride, 3-methyl-N-butyl-pyridinium chloride andbenzyldimethyl(tetradecyl)ammonium chloride. Substituent groups, (i.e. Rgroups), on the cations can be C₁, C₂, C₃, and C_(4;) these can besaturated or unsaturated. Examples of compounds which are ionic liquidsinclude, but are not limited to, 1-ethyl-3-methyl imidazolium chloride,1-ethyl-3-methyl imidazolium acetate, 1-butyl-3-methyl imidazoliumchloride, 1-allyl-3-methyl imidazolium chloride, zinc chloride/cholinechloride, 3-methyl-N-butyl-pyridinium chloride,benzyldimethyl(tetradecyl)ammonium chloride and1-methylimidazolehydrochloride. The 1-ethyl-3-methyl imidazolium acetateused in this work was obtained from Sigma Aldrich, Milwaukee.

In one embodiment cellulose is dissolved in a mixture of a dipolaraprotic agent and an ionic liquid. Mixtures of the dipolar aprotic agentand the ionic liquid dissolve cellulose over a wide temperature range.In one embodiment cellulose is dissolved in the range of 25° C. to 180°C. In another embodiment cellulose is dissolved over the range of 80° C.to 120° C. In yet another embodiment cellulose is dissolved over atemperature range of from 100° C. to 110° C. Dissolution of cellulosecan be conducted with or without stirring. The latter acceleratesdissolution of cellulose. Table 1 shows the dissolution of cellulose(10% weight add on of Peach® on total weight of mixture of dipolaraprotic agent and ionic liquid) in a mixture of dipolar aprotic agentsand ionic liquids at 105° C.; Table 2 shows the dissolution of cellulose(10% weight Peach® add on) in a mixture of dipolar aprotic agents andionic liquids at 105° C. with stirring. For purposes of thisapplication, cellulose is considered dissolved when the solution isvisually examined and is cloudy or clear. The dissolution of celluloseis further confirmed by casting the cellulose dope on a glass slide toform a film and regenerating the film in water. In the tables, molarratio refers to the ratio of the dipolar aprotic agent to the ionicliquid. For example a molar ratio of 10.27 for the mixture of DMSO andEMIMAc (1-ethyl-3-methyl imidazolium acetate) means that 10.27 moles ofDMSO and one mole of EMIMAc dissolve cellulose at 105° C. in one hour.

Cellulose is dissolved over a wide range of molar ratios of the dipolaraprotic solvent to the ionic liquid. For ionic liquids that are liquids,the calculated amount of dipolar aprotic solvent was added to the ionicliquid, mixed and a fixed quantity of cellulose was added. For ionicliquids that are solids, the ionic liquid was heated to melt the solid,the calculated amount of a dipolar_aprotic solvent was added to theionic liquid, mixed and a fixed quantity of cellulose was added. Heatingwas conducted in a sealed vial at 105° C. for samples that were notstirred and at 105° C. with occasional stirring with a spatula afteropening the heated sealed vial. In some cases dissolution was conductedas low as 25° C. if the solvent mixture is a solution at roomtemperature.

In some embodiments the molar ratio of dipolar aprotic intercyrstallineswelling agent to ionic liquid may be from 0.5 to 25 moles of dipolaraprotic intercrystalline swelling agent to 1 mole of ionic liquid. Insome embodiments the molar ratio of dipolar aprotic intercyrstallineswelling agent to ionic liquid may be from 0.5 to 15 moles of dipolaraprotic intercrystalline swelling agent to 1 mole of ionic liquid. Insome embodiments the molar ratio of dipolar aprotic intercyrstallineswelling agent to ionic liquid may be from 0.5 to 2 moles of dipolaraprotic intercrystalline swelling agent to 1 mole of ionic Liquid. Inone embodiment a molar ratio of 10.27 for the mixture of DMSO and EMIMAc(1-ethyl-3-methyl imidazolium acetate) dissolves cellulose in one hourat 105° C. In another embodiment a molar ratio of 1.25 for the mixtureof DMSO and EMIMCl (1-ethyl-3-methyl imidazolium chloride) dissolvescellulose at 105° C. in 20 hours. In one embodiment a molar ratio of 0.8for the mixture of DMSO and EMIMCl (1-ethyl-3-methyl imidazoliumchloride) dissolves cellulose in 45 minutes at 105° C. with stirring. Inanother embodiment a molar ratio of 1.7 for the mixture of DMAc andBMIMCl (1-butyl-3-methyl imidazolium chloride) dissolves cellulose at105° C. in 30 minutes with stirring.

In some embodiments the time of dissolution for mixtures of dipolaraprotic agents and ionic liquids may be 5 minutes to 24 hours. In someembodiments the time of dissolution for mixtures of dipolar aproticagents and ionic liquids may be 5 minutes to 1 hours.

Mixtures of the dipolar aprotic agents and ionic liquids have asurprising effect on viscosity and exhibit Newtonian flowcharacteristics. Viscosity was determined at a different shear rateswith a rotational rheometer from Bohlin (Viscometry Mode at roomtemperature) Table 4, 5 and 6 show the effect on viscosity (Pas, pascalseconds) at different shear rates (second⁻¹) of cellulose dissolved in amixture dipolar aprotic intercrystalline swelling agents and ionicliquids. The tables show that with increasing shear rate the viscositydecreases. This is particularly beneficial where throughput inmanufacturing is important since more weight per unit time can beachieved through the spinning head.

In another embodiment cellulose is dissolved in a mixture of a proticsolvent and an ionic liquid. Protic solvents include but are not limitedto water, low molecular alcohols such as methyl, ethyl, propyl, butyland amyl alcohol, ethylene glycol, acetic acid, quaternary ammoniumhydroxide, quaternary ammonium cations, methylamine, di- andtriethylamine and butylamine and mixtures thereof. For ionic liquidsthat are liquids, the calculated amount of protic agent was added to theionic liquid, mixed and a fixed quantity of cellulose was added. Forionic liquids that are solids, the ionic liquid was heated to melt thesolid, the calculated amount of protic solvent was added to the ionicliquid, mixed and a fixed quantity of cellulose was added. Heating wasconducted in a sealed vial at 105° C. for samples that were not stirredand at 105° C. with stirring. In some cases dissolution was conducted aslow as 25° C. if the ionic liquid and the protic agent are liquid atroom temperature.

Mixtures of the protic agent and the ionic liquid dissolve celluloseover a wide temperature range In one embodiment cellulose is dissolvedin the range of 25° C. to 180° C. In another embodiment cellulose isdissolved over the range of 80° C. to 120° C. In yet another embodimentcellulose is dissolved over a temperature range of from 100° C. to 110°C. Dissolution of cellulose can be conducted with or without stirring.The latter accelerates dissolution of cellulose. Table 3 shows thedissolution of cellulose in a mixture of protic solvents and ionicliquids at 105° C. For purposes of this application, cellulose isconsidered dissolved when the solution is visually examined and thesolution is cloudy or clear. In the table, molar ratio refers to theratio of the protic solvent to the ionic liquid. For example a molarratio of 0.13 for the mixture of acetic and EMIMCl (1-ethyl-3-methylimidazolium chloride) means that 0.13 moles of acetic acid and one moleof EMIMCl dissolve cellulose at 105° C. in two hours 105° C. The molarratio of protic intercyrstalline swelling agent to ionic liquid may befrom 0.05 to 1.5 moles of dipolar aprotic intercrystalline swellingagent to 1 mole of ionic liquid.

In some embodiments the dissolution time for a mixture of protic agentsand ionic liquids may be 5 minutes to 24 hours. In some embodiments thedissolution time for a mixture of protic agents and ionic liquids may be5 minutes to 5 hours. In some embodiments the dissolution time for amixture of protic agents and ionic liquids may be 5 minutes to 2 hours.In some embodiments the dissolution time for a mixture of protic agentsand ionic liquids may be 5 minutes to 1 hour.

Cellulose dissolved in the protic agent and the ionic liquid or thedipolar aprotic agent and the ionic liquid can be regenerated byprecipitating the cellulose in a liquid in which it is immiscible suchas water, alcohol, mixtures thereof, a mixture of a protic agent and anionic liquid, or with a high ratio of a protic or dipolar aprotic agentto the ionic liquid. Preferably the liquid non-solvent is miscible withwater but other non-solvents such methanol, ethanol, acetonitrile, anether such as furan or dioxane or a ketone can be used. The advantage ofwater is that the process avoids the use of a volatile organic compoundand regeneration does not require the use of volatile organic solvents.Thus the ionic liquid can be dried and reused after regeneration. In oneembodiment water is used as the non-solvent for regeneration of thecellulose. Mixtures of from 0% by weight non-solvent/solvent to about50% by weight non-solvent/solvent can be used for regenerating thecellulose from the ionic liquid solution. For example, up to a 50% byweight water and 50% by weight 1-ethyl-3-methyl imidazolium acetate canbe used in the regeneration process.

In the following tables the numbers in parenthesis are the grams ofmaterial. For example in Table 1 DMSO (8.25) means 8.25 grams of DMSO.

In table 3, two molar ratios are given for BTMAH. There is water inBTMAH. The first molar ratio is for moles of water to a mole of ionicliquid. The second is the molar ratio of water to BTMAH. BTMAH isBenzyltrimethylammonium hydroxide, 40% in water.

TABLE 1 Cellulose Dissolution In Ionic Liquids With Dipolar aproticAgents At 105° C. Dipolar Ionic aprotic Liquid, Molar Solubility, Agent(g) (g) Ratio 1 Hr. 2 Hr. 20 Hr. DMSO EMIMAc 10.27 yes (8.25) (1.75)DMSO EMIMAc 12.35 no dissolved (8.5) (1.5) in 5 hr. DMSO (9) EMIMAc 21no cloudy (1) DMSO (4) EMIMCl 1.25 cloudy (6) DMSO (5) EMIMCl 1.88incomplete (5) DMSO (8) EMIMCl 7.51 incomplete (2) DMSO (4) BMIMCl 1.49yes (6) DMSO BMIMCl 1.83 yes (4.5) (5.5) DMSO (5) BMIMCl 2.24 incompletein- incomplete (5) complete DMSO (8) BMIMCl 8.94 no no (2)

TABLE 2 Cellulose Dissolution in Ionic Liquids With Dipolar aproticAgents At 105° C. With Stirring Additive Ionic Liquid Molar ratioSolubility, 15 min. Solubility, 30 min. Solubility, 45 min. DMSO (3)EMIMCl (7) 0.8 yes DMSO (4) EMIMCl(6) 1.25 cloudy cloudy yes DMSO (5)EMIMCl (5) 1.88 incomplete incomplete incomplete DMAc (3.5) EMIMCl (6.5)0.91 cloudy cloudy yes DMAc (4) EMIMCl (6) 1.12 no mostly mostly DMF(3.5) EMIMCl (6.5) 1.08 mostly yes yes DMF (4) EMIMCl (6) 1.34 no nomostly NMP (4) EMIMCl (6) 0.99 Yes yes NMP (5) EMIMCl (5) 1.48 mostlyyes NMP (4.5) EMIMCl (5.5) 1.81 no no no DMSO (4.5) BMIMCl (5.5) 1.83Yes yes yes DMSO (5) BMIMCl (5) 2.24 incomplete incomplete incompleteDMAc (3.5) BMIMCl (6.5) 1.7 mostly yes DMAc (4) BMIMCl (6) 1.34 no noyes DMAc (4.5) BMIMCl (5.5) 1.64 no no incomplete DMF (3.5) BMIMCl (6.5)no no yes DMF (4) BMIMCl (6) no no incomplete NMP (3) BMIMCl (7) 0.76yes NMP (4) BMIMCl (6) 1.17 no yes yes NMP (4.5) BMIMCl (5.5) 1.44 noyes yes NMP (5) BMIMCl (5) 1.76 incomplete incomplete incomplete

TABLE 3 Cellulose Dissolution in Ionic Liquids With Protic Agents At105° C. Ionic Protic Additive Liquid Molar Ratio* 1 Hr. 2 Hr. 20 Hr.Water (0) EMIMCl yes yes yes (10) Water (0.5) EMIMCl 0.43 no yes yes(9.5) Water (0.75) EMIMCl 0.66 no no no (9.25) Acetic Acid (1) EMIMAc0.32 yes yes yes (9) Acetic Acid (1.5) EMIMAc 0.51 yes yes yes (8.5)Acetic Acid (2) EMIMAc 0.72 no No, 6 hr. not at 6 hr. (8) Acetic Acid(0.5) EMIMCl 0.13 No- yes yes (9.5) Acetic Acid (1) EMIMCl 0.27 no noincomplete (9) BTMAH(1) EMIMAc 0.61/0.05* yes (9) BTMAH(1.5) EMIMAc0.87/0.07* no yes (8.5) BTMAH(1.75) EMIMAc   1/.09* no 4 hr. (8.25)BTMAH(2) EMIMAc 1.38/0.11* incomplete incomplete incomplete (8) AceticAcid (0.5) EMIMCl 0.13 no yes (9.5) Acetic Acid (1) EMIMCl 0.27 no no50% (9) Water (0.25) BMIMCl 0.25 cloudy cloudy cloudy (9.75) Water (0.5)BMIMCl 0.51 incomplete incomplete incomplete (9.5) Acetic Acid BMIMCl0.07 Yes (a) Yes (b) Yes (c) (0.25) (9.75) Acetic Acid BMIMCl 0.15 no(a) Yes (b) Yes (c) (0.5) (9.5) Acetic Acid BMIMCl 0.24 cloudy cloudycloudy (0.75) (9.25) Acetic Acid BMIMCl 0.32 No (a) No (b) No (c) (1.0)(9.0) (a) solubility in 90 min. (b) solubility in 150 min. (c)solubility in 22 hr. *water/BTMAH

TABLE 4 Effect Of Shear Rate on Solution Viscosity 2% Peach ® 2% Peach ®pulp in pulp in EMIMAc + DMSO EMIMAc 1/9 Shear Rate Viscosity Viscosity0.15 18.44 0.27 0.27 18.28 0.28 0.48 17.75 0.32 0.86 16.91 0.31 1.5416.00 0.31 2.75 15.17 0.32 4.93 14.29 0.32 8.82 13.36 0.32 15.80 12.450.32 28.30 11.25 0.31 50.69 9.81 0.31 90.78 8.23 0.30 162.56 6.62 0.29291.11 5.10 0.27 521.40 3.83 0.24

TABLE 5 Effect Of Shear Rate on Solution Viscosity 1% 1% Peach ® 1%Peach ® pulp 1% Peach ® pulp 1% Peach ® Peach ® pulp in in in pulp inpulp in BMIMCl/NMP BMIMCl/DMSO BMIMCl/DMAc BMIMCl/DMF Shear BMIMCl 7/37/3 7/3 7/3 Rate Viscosity Viscosity Viscosity Viscosity Viscosity 0.1511.07 7.31 5.78 3.93 2.78 0.27 11.37 7.30 5.72 3.88 2.77 0.48 11.57 7.165.62 3.84 2.75 0.86 11.77 6.95 5.54 3.78 2.73 1.54 11.86 6.62 5.38 3.692.69 2.75 11.74 6.27 5.16 3.56 2.63 4.93 11.69 5.89 4.90 3.42 2.55 8.8211.37 5.47 4.54 3.24 2.43 15.80 11.20 4.96 4.14 2.98 2.27 28.30 11.234.39 3.68 2.70 2.08 50.69 11.26 3.80 3.26 2.41 1.88 90.78 11.24 3.212.85 2.11 1.65 162.56 11.10 2.66 2.42 1.80 1.42 291.11 10.70 2.18 2.011.51 1.20 521.40 9.34 1.75 1.64 1.25 0.99

TABLE 6 Effect Of Shear Rate on Solution Viscosity 1% 1% Peach ® 1%Peach ® pulp 1% Peach ® Peach ® pulp in in pulp in pulp in EMIMCl/NMPEMIMCl/DMSO EMIMCl/DMF Shear EMIMCl 7/3 7/3 7/3 Rate Viscosity ViscosityViscosity Viscosity 0.15 21.27 4.11 4.23 1.48 0.27 21.44 4.05 4.17 1.520.48 21.36 3.95 4.06 1.50 0.86 21.22 3.83 3.97 1.46 1.54 20.75 3.68 3.871.42 2.75 19.84 3.55 3.75 1.37 4.93 18.98 3.41 3.58 1.33 8.82 17.93 3.233.39 1.27 15.80 16.92 3.01 3.12 1.21 28.30 16.13 2.72 2.81 1.14 50.6915.49 2.41 2.48 1.05 90.78 14.75 2.12 2.15 0.95 162.56 13.73 1.81 1.840.84 291.11 12.05 1.52 1.53 0.73 521.40 9.62 1.26 1.26 0.63

EXAMPLE 1

A dope for forming films was made by dissolving a Kraft pulp, Peach®pulp having an average degree of polymerization of about 760 and ahemicellulose content of about 12% (6.7% xylan, 5.2% mannan) in1-ethyl-3-methylimidazolium acetate/water or benzyltrimethyl ammoniumhydroxide (BTMAH) mixture at 105° C. with stirring. The solidconcentration in the dope was about 13.2% by weight. The dope was caston a glass plate to make film, which is regenerated in water, washed,air dried for analysis. X-ray diffraction indicated that samples treatedwith IL containing 10% H2O still has cellulose I structure while otherfilms have cellulose II structure (regenerated form). X-ray diffractionmeasurements of fiber samples were recorded on a Shimadadzu X-raydiffractometer using Ni-filtered, CuKα radiation, a voltage of 40 k Vand a current of 40 mA. The scanning rate employed was 5 degrees per minover a 5 degree to 40 degree 2θ (diffraction angle) range. Thecrystallinity index was determined by Segal's formula (Segal L C, MartinA E, Conrad C M. 1959 Textile Res J. 29: 786-794). The % CrystallinityIndex was calculated as ((I₀₂₀−I_(am))/I₀₂₀)×100, where I₀₂₀=intensityat Lowest 2θ value near 18 degrees. The properties of the film are givenbelow.

Cellulose Solution Pulp Film Properties Cellulose R10 Xylan MannanCrystallinity Wt % cosolvent % R18 % % % index 13.2 10% H2O 83 87 4.224.26 0.67 13.2  5% H2O 83 87 5.66 4.88 0.57 13.2 10% 83 87 5.53 4.750.58 BTMAH

EXAMPLE 2

A dope for forming films was made by dissolving cellulose acetate, (6.6g) and 6.6 g of a craft pulp, Peach® having an average degree ofpolymerization of about 760 and a hemicellulose content of about 12%(6.7% xylan, 5.2% mannan) in 1-ethyl-3-methylimidazolium acetate/DMSOmixture (43.4 g/43.4 g) at 105° C. with stirring. The solidconcentration in the dope was about 13.2% by weight. The dope was caston a glass plate to make film, which is regenerated in water, washed,air dried for analysis. Cellulose acetate lowers the film crystallinity.

As used in this application one method for measuring the degradedshorter molecular weight components in the pulp is by the R₁₈ and R₁₀content as described in TAPPI 235. R₁₀ represents the residualundissolved material that is left extraction of the pulp with 10 percentby weight caustic and R₁₈ represents the residual amount of undissolvedmaterial left after extraction of the pulp with an 18% caustic solution.Generally, in a 10% caustic solution, hemicellulose and chemicallydegraded short chain cellulose are dissolved and removed in solution. Incontrast, generally only hemicellulose is dissolved and removed in an18% caustic solution. Thus, the difference between the R₁₀ value and theR₁₈ value, (Δ R=R₁₈−R₁₀), represents the amount of chemically degradedshort chained cellulose that is present in the pulp sample.Hemicellulose is measured as the sum of the xylan and mannan content andwas determined by the method described below for sugar analysis. Asdefined herein degree of polymerization (abbreviated as D.P.) refers tothe number of anhydro-D-glucose units in the cellulose chain. D.P. wasdetermined by ASTM Test 1795-96.

The properties of the film are given below.

Film Properties Solution Pulp Properties Crystal- Cellulose R10 R18Xylan Mannan Insoluble linity Wt % DP % % % % % index 6.6 760 83 87 1.701.68 0.4 0.51

EXAMPLE 3

A dope for forming filaments was made by dissolving a wood chip in1-ethyl-3-methylimidazolium acetate (EMIMAc) or its mixture with DMSOmixture at 105° C. with stirring. The chip concentration in the dope wasabout 13% by weight. The dope was cast on a glass plate to make film,which is regenerated in water, washed, air dried for x-ray analysis.Wood chips, approximately 1.3 g dissolved in a mixture of 5 g ofEMIMAc/5 g DMSO had the lowest crystallinity (0.27), while those treatedwith EMIMAc had a crystallinity index of 0.35 and the untreated chip hasa crystallinity index of 0.60.This would suggest that relative to thecrystallinity index of the chip, the mixed solvent system of EMIMAc/DMSOhas a higher impact on the crystallinity region than does the EMIMAcalone.

Sugar Analysis

This method is applicable for the preparation and analysis of pulp andwood samples for the determination of the amounts of the following pulpsugars: fucose, arabinose, galactose, rhamnose, glucose, xylose andmannose using high performance anion exchange chromatography and pulsedamperometric detection (HPAEC/PAD).

Summary of Method

Polymers of pulp sugars are converted to monomers by hydrolysis usingsulfuric acid. Samples are ground, weighed, hydrolyzed, diluted to200-mL final volume, filtered, diluted again (1.0 mL+8.0 mL H₂O) inpreparation for analysis by HPAEC/PAD.

Sampling, Sample Handling and Preservation

Wet samples are air-dried or oven-dried at 25±5° C.

Equipment Required

Autoclave, Market Forge, Model # STM-E, Serial # C-1808

100×10 mL Polyvials, septa, caps, Dionex Cat #55058

Gyrotory Water-Bath Shaker, Model G76 or some equivalent.

Balance capable of weighing to ±0.01 mg, such as Mettler HL52 AnalyticalBalance.

Intermediate Thomas-Wiley Laboratory Mill, 40 mesh screen.

NAC 1506 vacuum oven or equivalent.

0.45-μ GHP filters, Gelman type A/E, (4.7-cm glass fiber filter discs,without organic binder)

Heavy-walled test tubes with pouring lip, 2.5×20 cm.

Comply SteriGage Steam Chemical Integrator

GP 50 Dionex metal-free gradient pump with four solvent inlets

Dionex ED 40 pulsed amperometric detector with gold working electrodeand solid state reference electrode

Dionex autosampler AS 50 with a thermal compartment containing thecolumns, the ED 40 cell and the injector loop

Dionex PC10 Pneumatic Solvent Addition apparatus with 1-L plastic bottle

3 2-L Dionex polyethylene solvent bottles with solvent outlet and heliumgas inlet caps

CarboPac PA1 (Dionex P/N 035391) ion-exchange column, 4 mm×250 mm

CarboPac PA1 guard column (Dionex P/N 043096), 4 mm×50 mm

Millipore solvent filtration apparatus with Type HA 0.45u filters orequivalent

Reagents Required

All references to H₂O is Millipore H₂O

72% Sulfuric Acid Solution (H2SO4)—Transfer 183 mL of water into a 2-LErlenmeyer flask. Pack the flask in ice in a Rubbermaid tub in a hoodand allow the flask to cool. Slowly and cautiously pour, with swirling,470 mL of 96.6% H₂SO₄ into the flask. Allow solution to cool. Carefullytransfer into the bottle holding 5-mL dispenser. Set dispenser for 1 mL.

JT Baker 50% sodium hydroxide solution, Cat. No. Baker 3727-017[1310-73-2]

Dionex sodium acetate, anhydrous (82.0±0.5 grams/1 L H₂O), Cat. No.59326, [127-09-3].

Standards

Internal Standards

Fucose is used for the kraft and dissolving pulp samples.2-Deoxy-D-glucose is used for the wood pulp samples.

Fucose, internal standard. 12.00±0.005 g of Fucose, Sigma Cat. No. F2252, [2438-80-4], is dissolved in 200.0 mL H₂O giving a concentrationof 60.00±0.005 mg/mL. This standard is stored in the refrigerator.

2-Deoxy-D-glucose, internal standard. 12.00±0.005 g of2-Deoxy-D-glucose, Fluka Cat. No. 32948 g [101-77-9] is dissolved in200.0 mL H₂O giving a concentration of 60.00±0.005 mg/mL. This standardis stored in the refrigerator.

Kraft Pulp Stock Standard Solution

Kraft Pulp Sugar Standard Concentrations

Sugar Manufacturer Purity g/200 mL Arabinose Sigma 99% 0.070 GalactoseSigma 99% 0.060 Glucose Sigma 99% 4.800 Xylose Sigma 99% 0.640 MannoseSigma 99% 0.560

Kraft Pulp Working Solution

Weigh each sugar separately to 4 significant digits and transfer to thesame 200-mL volumetric flask. Dissolve sugars in a small amount ofwater. Take to volume with water, mix well, and transfer contents to twoclean, 4-oz. amber bottles. Label and store in the refrigerator. Makeworking standards as in the following table.

Pulp Sugar Standard Concentrations for Kraft Pulps

Fucose mL/200 mL mL/200 mL mL/200 mL mL/200 mL mL/200 mL 0.70 1.40 2.102.80 3.50 Sugar mg/mL ug/mL ug/mL ug/mL ug/mL ug/mL Fucose 60.00 300.00300.00 300.00 300.00 300.00 Arabinose 0.36 1.2 2.5 3.8 5.00 6.508Galactose 0.30 1.1 2.2 3.30 4.40 5.555 Glucose 24.0 84 168.0 252.0 336.0420.7 Xylose 3.20 11 22.0 33.80 45.00 56.05 Mannose 2.80 9.80 19.0 29.039.0 49.07

Dissolving Pulp Stock Standard Solution

Dissolving Pulp Sugar Standard Concentrations

Sugar Manufacturer Purity g/100 mL Glucose Sigma 99% 6.40 Xylose Sigma99% 0.120 Mannose Sigma 99% 0.080

Dissolving Pulp Working Solution

Weigh each sugar separately to 4 significant digits and transfer to thesame 200-mL volumetric flask. Dissolve sugars in a small amount ofwater. Take to volume with water, mix well, and transfer contents to twoclean, 4-oz. amber bottles. Label and store in the refrigerator. Makeworking standards as in the following table.

Pulp Sugar Standard Concentrations for Dissolving Pulps

Fucose mL/200 mL mL/200 mL mL/200 mL mL/200 mL mL/200 mL 0.70 1.40 2.102.80 3.50 Sugar mg/mL ug/mL ug/mL ug/mL ug/mL ug/mL Fucose 60.00 300.00300.00 300.00 300.00 300.00 Glucose 64.64 226.24 452.48 678.72 904.961131.20 Xylose 1.266 4.43 8.86 13.29 17.72 22.16 Mannose 0.8070 2.825.65 8.47 11.30 14.12

Wood Pulp Stock Standard Solution

Wood Pulp Sugar Standard Concentrations

Sugar Manufacturer Purity g/200 mL Fucose Sigma 99% 12.00 Rhamnose Sigma99% 0.0701

Dispense 1 mL of the fucose solution into a 200-mL flask and bring tofinal volume.

Final concentration will be 0.3 mg/mL.

Wood Pulp Working Solution

Use the Kraft Pulp Stock solution and the fucose and rhamnose stocksolutions. Make working standards as in the following table.

Pulp Sugar Standard Concentrations for Kraft Pulps

2-Deoxy-D-glucose mL/200 mL mL/200 mL mL/200 mL mL/200 mL mL/200 mL 0.701.40 2.10 2.80 3.50 Sugar mg/mL ug/mL ug/mL ug/mL ug/mL ug/mL 2-DG 60.00300.00 300.00 300.00 300.00 300.00 Fucose 0.300 1.05 2.10 3.15 4.20 6.50Arabinose 0.36 1.2 2.5 3.8 5.00 6.508 Galactose 0.30 1.1 2.2 3.30 4.405.555 Rhamnose 0.3500 1.225 2.450 3.675 4.900 6.125 Glucose 24.00 84168.0 252.0 336.0 420.7 Xylose 3.20 11 22.0 33.80 45.00 56.05 Mannose2.80 9.80 19.0 29.0 39.0 49.07

Procedure

Sample Preparation

Grind 0.2±05 g sample with Wiley Mill 40 Mesh screen size. Transfer ˜200mg of sample into 40-mL Teflon container and cap. Dry overnight in thevacuum oven at 50° C. Add 1.0 ml 72% H₂SO₄ to test tube with theBrinkman dispenser. Stir and crush with the rounded end of a glass orTeflon stirring rod for one minute. Turn on heat for Gyrotory Water-BathShaker. The settings are as follows:

Heat: High

Control Thermostat: 7° C.

Safety thermostat: 25° C.

Speed: Off

Shaker: Off

Place the test tube rack in gyrotory water-bath shaker. Stir each sample3 times, once between 20-40 min, again between 40-60 min, and againbetween 60-80 min. Remove the sample after 90 min. Dispense 1.00 mL ofinternal standard (Fucose) into Kraft samples.

Tightly cover samples and standard flasks with aluminum foil to be surethat the foil does not come off in the autoclave.

Place a Comply SteriGage Steam Chemical Integrator on the rack in theautoclave. Autoclave for 60 minutes at a pressure of 14-16 psi (95-105kPa) and temperature>260° F. (127° C.).

Remove the samples from the autoclave. Cool the samples. Transfersamples to the 200-mL volumetric flasks. Add 2-deoxy-D-glucose to woodsamples. Bring the flask to final volume with water.

For Kraft and Dissolving pulp samples:

Filter an aliquot of the sample through GHP 0.45μ filter into a 16-mLamber vial.

For Wood pulp samples:

Allow particulates to settle. Draw off approximately 10 mL of samplefrom the top, trying not to disturb particles and filter the aliquot ofthe sample through GHP 0.45μ filter into a 16-mL amber vial. Transferthe label from the volumetric flask to the vial. Add 1.00 mL aliquot ofthe filtered sample with to 8.0 mL of water in the Dionex vial.

Samples are run on the Dionex AS/500 system. See Chromatographyprocedure below.

Chromatography Procedure

Solvent preparation

Solvent A is distilled and deionized water (18 meg-ohm), sparged withhelium while stirring for a minimum of 20 minutes, before installingunder a blanket of helium, which is to be maintained regardless ofwhether the system is on or off.

Solvent B is 400 mM NaOH. Fill Solvent B bottle to mark with water andsparge with helium while stirring for 20 minutes. Add appropriate amountof 50% NaOH.

(50.0 g NaOH/100 g solution)*(1 mol NaOH/40.0 g NaOH)*(1.53 g solution/1mL solution)*(1000 mL solution/1 L solution)=19.1 M NaOH in thecontainer of 50/50 w/w NaOH.

0.400 M NaOH*(1000 mL H₂O/19.1 M NaOH)=20.8 mL NaOH

Round 20.8 mL down for convenience:

19.1 M*(20.0 mL x mL)=0.400 M NaOH

x mL=956 mL

Solvent D is 200 mM sodium acetate. Using 18 meg-ohm water, addapproximately 450 mL deionized water to the Dionex sodium acetatecontainer. Replace the top and shake until the contents are completelydissolved. Transfer the sodium acetate solution to a 1-L volumetricflask. Rinse the 500-mL sodium acetate container with approximately 100mL water, transferring the rinse water into the volumetric flask. Repeatrinse twice.

After the rinse, fill the contents of the volumetric flask to the 1-Lmark with water.

Thoroughly mix the eluent solution. Measure 360±10 mL into a 2-Lgraduated cylinder.

Bring to 1800±10 mL. Filter this into a 2000-mL sidearm flask using theMillipore filtration apparatus with a 0.45 pm, Type HA membrane. Addthis to the solvent D bottle and sparge with helium while stirring for20 minutes.

The postcolumn addition solvent is 300 mM NaOH. This is added postcolumnto enable the detection of sugars as anions at pH>12.3. Transfer 15±0.5ML of 50% NaOH to a graduated cylinder and bring to 960±10 mL in water.

(50.0 g NaOH/100 g Solution)*(1 mol NaOH/40.0 g NaOH)*(1.53 g Solution/1mL Solution)(1000 mL Solution/1 L solution)=19.1 M NaOH in the containerof 50/50 w/w NaOH.

0.300 M NaOH*(1000ml H₂O/19.1 M NaOH)=15.7 mL NaOH

Round 15.7 mL down:

19.1M*(15.0 mL/x mL)=0.300 M NaOH

x mL=956 mL

(Round 956 mL to 960 mL. As the pH value in the area of 0.300 M NaOH issteady, an exact 956 mL of water is not necessary.)

Set up the AS 50 schedule.

Injection volume is 5 uL for all samples, injection type is “Full”, cutvolume is 10 uL, syringe speed is 3, all samples and standards are ofSample Type “Sample”. Weight and Int. Std. values are all set equal to1.

Run the five standards at the beginning of the run in the followingorder:

STANDARD A1 DATE

STANDARD B1 DATE

STANDARD C1 DATE

STANDARD D1 DATE

STANDARD E1 DATE

After the last sample is run, run the mid-level standard again as acontinuing calibration verification

Run the control sample at any sample spot between the beginning andending standard runs.

Run the samples.

Calculations

Calculations for Weight Percent of the Pulp Sugars

${{Normalized}\mspace{14mu} {area}\mspace{14mu} {for}\mspace{14mu} {sugar}} = \frac{( {{Area}\mspace{14mu} {sugar}} )*( {{µg}\text{/}{mL}\mspace{14mu} {fucose}} )}{( {{Area}\mspace{14mu} {Fucose}} )}$

$I\; S\mspace{14mu} {Corrected}\mspace{14mu} {sugar}\mspace{14mu} {{amount}( {{{µg}\text{/}{mL}} = \frac{\begin{pmatrix}{( {{Normalized}\mspace{14mu} {area}\mspace{14mu} {for}\mspace{14mu} {sugar}} ) -} \\({intercept})\end{pmatrix}}{({slope})}} }$

${{Monomer}\mspace{14mu} {Sugar}\mspace{14mu} {Weight}\mspace{14mu} \%} = {\frac{\begin{matrix}{{I\; S} -} \\{{Corrected}\mspace{14mu} {sugar}\mspace{14mu} {{amt}( {{µg}\text{/}{mL}} )}}\end{matrix}}{{Sample}\mspace{14mu} {{wt}.({mg})}}*20}$

Example for arabinose:

$\begin{matrix}{{{Monomer}\mspace{14mu} {Sugar}\mspace{14mu} {Weight}\mspace{14mu} \%} = {\frac{0.15\mspace{14mu} {µg}\text{/}{mL}\mspace{14mu} {arabinose}}{70.71\mspace{14mu} {mg}\mspace{14mu} {arabinose}}*20}} \\{= {0.043\%}}\end{matrix}$

Polymer Weight %=(Weight % of Sample sugar)*(0.88)

Example for arabinan:

Polymer Sugar Weight %=(0.043 wt %)*(0.88)=0.038 Weight

Note: Xylose and arabinose amounts are corrected by 88% and fucose,galactose, rhamnose, glucose, and mannose are corrected by 90%.

Report results as percent sugars on an oven-dried basis.

The embodiments of this invention, including the examples, are exemplaryof numerous embodiments that may be made of this invention. It iscontemplated that numerous other configurations of the process may beused and the equipment used in the process may be selected from numeroussources other than those specifically disclosed. In short, it is theapplicant's intention that the scope of the patent issuing herefrom willbe limited only by the scope of the appended claims

1. A method for dissolving cellulose comprising admixing a cellulosebased raw material with a mixture of a protic intercrystalline swellingagent and an ionic liquid at a temperature of 25° C. to 180° C. for atime sufficient to dissolve the cellulose based raw material, whereinthe molar ratio of protic intercyrstalline swelling agent to ionicliquid may be 0.05 to 1.5 moles of protic intercrystalline swellingagent to 1 mole of ionic liquid.
 2. The method of claim 1 wherein thecellulose based raw material is wood chips, wood pulp, kenaf or straw.3. The method of claim 3 wherein the wood pulp is chemical wood pulp,kraft wood pulp, sulfite wood pulp, mechanical wood pulp,thermomechanical wood pulp, or chemithermomechanical wood pulp.
 4. Themethod of claim 1 wherein the temperature range is 80° C. to 120° C. 5.The method of claim 1 wherein the temperature range is 100° C. to 110°C.
 6. The method of claim 1 wherein the time is 5 minutes to 24 hours.7. The method of claim 1 wherein the time is 5 minutes to 5 hours. 8.The method of claim 1 wherein the time is 5 minutes to 2 hours.
 9. Themethod of claim 1 wherein the time is 5 minutes to 1 hour.
 10. Themethod of claim 1 wherein the protic intercrystalline swelling agent iswater, methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol,amyl alcohol, ethylene glycol, acetic acid, quaternary ammoniumhydroxide, quaternary ammonium cations, methylamine, di- andtriethylamine and butylamine and mixtures thereof. 11 The method ofclaim 1 wherein the ionic liquid is 1-ethyl-3-methyl imidazoliumchloride, 1-ethyl-3-methyl imidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-allyl-3-methyl imidazolium chloride, zincchloride/choline chloride, 3-methyl-N-butyl-pyridinium chloride,benzyldimethyl(tetradecyl)ammonium chloride or1-methylimidazolehydrochloride, or mixtures thereof.
 12. The method ofclaim 1 further comprising regenerating the dissolved cellulose.